//// I2Cdev library collection - Main I2C device class
//// Abstracts bit and byte I2C R/W functions into a convenient class
//// 11/1/2011 by Jeff Rowberg <jeff@rowberg.net>
////
//// Changelog:
////     2011-11-01 - fix write*Bits mask calculation (thanks sasquatch @ Arduino forums)
////     2011-10-03 - added automatic Arduino version detection for ease of use
////     2011-10-02 - added Gene Knight's NBWire TwoWire class implementation with small modifications
////     2011-08-31 - added support for Arduino 1.0 Wire library (methods are different from 0.x)
////     2011-08-03 - added optional timeout parameter to read* methods to easily change from default
////     2011-08-02 - added support for 16-bit registers
////                - fixed incorrect Doxygen comments on some methods
////                - added timeout value for read operations (thanks mem @ Arduino forums)
////     2011-07-30 - changed read/write function structures to return success or byte counts
////                - made all methods static for multi-device memory savings
////     2011-07-28 - initial release
//
///* ============================================
//I2Cdev device library code is placed under the MIT license
//Copyright (c) 2011 Jeff Rowberg
//
//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:
//
//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.
//
//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.
//===============================================
//*/
//
//#include "I2Cdev.h"
//
//#if I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE
//    // NBWire implementation based heavily on code by Gene Knight <Gene@Telobot.com>
//    // Originally posted on the Arduino forum at http://arduino.cc/forum/index.php/topic,70705.0.html
//    // Originally offered to the i2cdevlib project at http://arduino.cc/forum/index.php/topic,68210.30.html
//    TwoWire Wire;
//#endif
//
///** Default constructor.
// */
//I2Cdev::I2Cdev() {
//}
//
///** Read a single bit from an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param bitNum Bit position to read (0-7)
// * @param data Container for single bit value
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (true = success)
// */
//int8_t I2Cdev::readBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t *data, uint16_t timeout) {
//    uint8_t b;
//    uint8_t count = readByte(devAddr, regAddr, &b, timeout);
//    *data = b & (1 << bitNum);
//    return count;
//}
//
///** Read a single bit from a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param bitNum Bit position to read (0-15)
// * @param data Container for single bit value
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (true = success)
// */
//int8_t I2Cdev::readBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t *data, uint16_t timeout) {
//    uint16_t b;
//    uint8_t count = readWord(devAddr, regAddr, &b, timeout);
//    *data = b & (1 << bitNum);
//    return count;
//}
//
///** Read multiple bits from an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param bitStart First bit position to read (0-7)
// * @param length Number of bits to read (not more than 8)
// * @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (true = success)
// */
//int8_t I2Cdev::readBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t *data, uint16_t timeout) {
//    // 01101001 read byte
//    // 76543210 bit numbers
//    //    xxx   args: bitStart=4, length=3
//    //    010   masked
//    //   -> 010 shifted
//    uint8_t count, b;
//    if ((count = readByte(devAddr, regAddr, &b, timeout)) != 0) {
//        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
//        b &= mask;
//        b >>= (bitStart - length + 1);
//        *data = b;
//    }
//    return count;
//}
//
///** Read multiple bits from a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param bitStart First bit position to read (0-15)
// * @param length Number of bits to read (not more than 16)
// * @param data Container for right-aligned value (i.e. '101' read from any bitStart position will equal 0x05)
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (1 = success, 0 = failure, -1 = timeout)
// */
//int8_t I2Cdev::readBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t *data, uint16_t timeout) {
//    // 1101011001101001 read byte
//    // fedcba9876543210 bit numbers
//    //    xxx           args: bitStart=12, length=3
//    //    010           masked
//    //           -> 010 shifted
//    uint8_t count;
//    uint16_t w;
//    if ((count = readWord(devAddr, regAddr, &w, timeout)) != 0) {
//        uint16_t mask = ((1 << length) - 1) << (bitStart - length + 1);
//        w &= mask;
//        w >>= (bitStart - length + 1);
//        *data = w;
//    }
//    return count;
//}
//
///** Read single byte from an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param data Container for byte value read from device
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (true = success)
// */
//int8_t I2Cdev::readByte(uint8_t devAddr, uint8_t regAddr, uint8_t *data, uint16_t timeout) {
//    return readBytes(devAddr, regAddr, 1, data, timeout);
//}
//
///** Read single word from a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to read from
// * @param data Container for word value read from device
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Status of read operation (true = success)
// */
//int8_t I2Cdev::readWord(uint8_t devAddr, uint8_t regAddr, uint16_t *data, uint16_t timeout) {
//    return readWords(devAddr, regAddr, 1, data, timeout);
//}
//
///** Read multiple bytes from an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr First register regAddr to read from
// * @param length Number of bytes to read
// * @param data Buffer to store read data in
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Number of bytes read (0 indicates failure)
// */
//int8_t I2Cdev::readBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t *data, uint16_t timeout) {
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print("I2C (0x");
//        Serial.print(devAddr, HEX);
//        Serial.print(") reading ");
//        Serial.print(length, DEC);
//        Serial.print(" bytes from 0x");
//        Serial.print(regAddr, HEX);
//        Serial.print("...");
//    #endif
//
//    int8_t count = 0;
//
//    Wire.beginTransmission(devAddr);
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.send(regAddr);
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        Wire.write(regAddr);
//    #endif
//    Wire.endTransmission();
//
//    Wire.beginTransmission(devAddr);
//    Wire.requestFrom(devAddr, length);
//
//    uint32_t t1 = millis();
//    for (; Wire.available() && (timeout == 0 || millis() - t1 < timeout); count++) {
//        #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//            data[count] = Wire.receive();
//        #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//            data[count] = Wire.read();
//        #endif
//        #ifdef I2CDEV_SERIAL_DEBUG
//            Serial.print(data[count], HEX);
//            if (count + 1 < length) Serial.print(" ");
//        #endif
//    }
//    if (timeout > 0 && millis() - t1 >= timeout && count < length) count = -1; // timeout
//
//    Wire.endTransmission();
//
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print(". Done (");
//        Serial.print(count, DEC);
//        Serial.println(" read).");
//    #endif
//
//    return count;
//}
//
///** Read multiple words from a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr First register regAddr to read from
// * @param length Number of words to read
// * @param data Buffer to store read data in
// * @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
// * @return Number of words read (0 indicates failure)
// */
//int8_t I2Cdev::readWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t *data, uint16_t timeout) {
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print("I2C (0x");
//        Serial.print(devAddr, HEX);
//        Serial.print(") reading ");
//        Serial.print(length, DEC);
//        Serial.print(" words from 0x");
//        Serial.print(regAddr, HEX);
//        Serial.print("...");
//    #endif
//
//    int8_t count = 0;
//
//    Wire.beginTransmission(devAddr);
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.send(regAddr);
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        Wire.write(regAddr);
//    #endif
//    Wire.endTransmission();
//
//    Wire.beginTransmission(devAddr);
//    Wire.requestFrom(devAddr, (uint8_t)(length * 2)); // length=words, this wants bytes
//
//    uint32_t t1 = millis();
//    bool msb = true; // starts with MSB, then LSB
//    for (; Wire.available() && count < length && (timeout == 0 || millis() - t1 < timeout);) {
//        if (msb) {
//            // first byte is bits 15-8 (MSb=15)
//            #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//                data[count] = Wire.receive() << 8;
//            #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//                data[count] = Wire.read() << 8;
//            #endif
//        } else {
//            // second byte is bits 7-0 (LSb=0)
//            #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//                data[count] |= Wire.receive();
//            #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//                data[count] |= Wire.read();
//            #endif
//            #ifdef I2CDEV_SERIAL_DEBUG
//                Serial.print(data[count], HEX);
//                if (count + 1 < length) Serial.print(" ");
//            #endif
//            count++;
//        }
//        msb = !msb;
//    }
//    if (timeout > 0 && millis() - t1 >= timeout && count < length) count = -1; // timeout
//
//    Wire.endTransmission();
//
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print(". Done (");
//        Serial.print(count, DEC);
//        Serial.println(" read).");
//    #endif
//
//    return count;
//}
//
///** write a single bit in an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to write to
// * @param bitNum Bit position to write (0-7)
// * @param value New bit value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t data) {
//    uint8_t b;
//    readByte(devAddr, regAddr, &b);
//    b = (data != 0) ? (b | (1 << bitNum)) : (b & ~(1 << bitNum));
//    return writeByte(devAddr, regAddr, b);
//}
//
///** write a single bit in a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to write to
// * @param bitNum Bit position to write (0-15)
// * @param value New bit value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeBitW(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint16_t data) {
//    uint16_t w;
//    readWord(devAddr, regAddr, &w);
//    w = (data != 0) ? (w | (1 << bitNum)) : (w & ~(1 << bitNum));
//    return writeWord(devAddr, regAddr, w);
//}
//
///** Write multiple bits in an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to write to
// * @param bitStart First bit position to write (0-7)
// * @param length Number of bits to write (not more than 8)
// * @param data Right-aligned value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t data) {
//    //      010 value to write
//    // 76543210 bit numbers
//    //    xxx   args: bitStart=4, length=3
//    // 00011100 mask byte
//    // 10101111 original value (sample)
//    // 10100011 original & ~mask
//    // 10101011 masked | value
//    uint8_t b;
//    if (readByte(devAddr, regAddr, &b) != 0) {
//        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
//        data <<= (bitStart - length + 1); // shift data into correct position
//        data &= mask; // zero all non-important bits in data
//        b &= ~(mask); // zero all important bits in existing byte
//        b |= data; // combine data with existing byte
//        return writeByte(devAddr, regAddr, b);
//    } else {
//        return false;
//    }
//}
//
///** Write multiple bits in a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register regAddr to write to
// * @param bitStart First bit position to write (0-15)
// * @param length Number of bits to write (not more than 16)
// * @param data Right-aligned value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeBitsW(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint16_t data) {
//    //              010 value to write
//    // fedcba9876543210 bit numbers
//    //    xxx           args: bitStart=12, length=3
//    // 0001110000000000 mask byte
//    // 1010111110010110 original value (sample)
//    // 1010001110010110 original & ~mask
//    // 1010101110010110 masked | value
//    uint16_t w;
//    if (readWord(devAddr, regAddr, &w) != 0) {
//        uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
//        data <<= (bitStart - length + 1); // shift data into correct position
//        data &= mask; // zero all non-important bits in data
//        w &= ~(mask); // zero all important bits in existing word
//        w |= data; // combine data with existing word
//        return writeWord(devAddr, regAddr, w);
//    } else {
//        return false;
//    }
//}
//
///** Write single byte to an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register address to write to
// * @param data New byte value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeByte(uint8_t devAddr, uint8_t regAddr, uint8_t data) {
//    return writeBytes(devAddr, regAddr, 1, &data);
//}
//
///** Write single word to a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr Register address to write to
// * @param data New word value to write
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeWord(uint8_t devAddr, uint8_t regAddr, uint16_t data) {
//    return writeWords(devAddr, regAddr, 1, &data);
//}
//
///** Write multiple bytes to an 8-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr First register address to write to
// * @param length Number of bytes to write
// * @param data Buffer to copy new data from
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeBytes(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint8_t* data) {
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print("I2C (0x");
//        Serial.print(devAddr, HEX);
//        Serial.print(") writing ");
//        Serial.print(length, DEC);
//        Serial.print(" bytes to 0x");
//        Serial.print(regAddr, HEX);
//        Serial.print("...");
//    #endif
//    uint8_t status = 0;
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.beginTransmission(devAddr);
//        Wire.send((uint8_t) regAddr); // send address
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        Wire.beginTransmission(devAddr);
//        Wire.write((uint8_t) regAddr); // send address
//    #endif
//    for (uint8_t i = 0; i < length; i++) {
//        #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//            Wire.send((uint8_t) data[i]);
//        #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//            Wire.write((uint8_t) data[i]);
//        #endif
//        #ifdef I2CDEV_SERIAL_DEBUG
//            Serial.print(data[i], HEX);
//            if (i + 1 < length) Serial.print(" ");
//        #endif
//    }
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.endTransmission();
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        status = Wire.endTransmission();
//    #endif
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.println(". Done.");
//    #endif
//    return status == 0;
//}
//
///** Write multiple words to a 16-bit device register.
// * @param devAddr I2C slave device address
// * @param regAddr First register address to write to
// * @param length Number of words to write
// * @param data Buffer to copy new data from
// * @return Status of operation (true = success)
// */
//bool I2Cdev::writeWords(uint8_t devAddr, uint8_t regAddr, uint8_t length, uint16_t* data) {
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.print("I2C (0x");
//        Serial.print(devAddr, HEX);
//        Serial.print(") writing ");
//        Serial.print(length, DEC);
//        Serial.print(" words to 0x");
//        Serial.print(regAddr, HEX);
//        Serial.print("...");
//    #endif
//    uint8_t status = 0;
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.beginTransmission(devAddr);
//        Wire.send(regAddr); // send address
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        Wire.beginTransmission(devAddr);
//        Wire.write(regAddr); // send address
//    #endif
//    for (uint8_t i = 0; i < length * 2; i++) {
//        #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//            Wire.send((uint8_t)(data[i++] >> 8)); // send MSB
//            Wire.send((uint8_t)data[i]);          // send LSB
//        #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//            Wire.write((uint8_t)(data[i++] >> 8)); // send MSB
//            Wire.write((uint8_t)data[i]);          // send LSB
//        #endif
//        #ifdef I2CDEV_SERIAL_DEBUG
//            Serial.print(data[i], HEX);
//            if (i + 1 < length) Serial.print(" ");
//        #endif
//    }
//    #if ((I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO < 100) || I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE)
//        Wire.endTransmission();
//    #elif (I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE && ARDUINO >= 100)
//        status = Wire.endTransmission();
//    #endif
//    #ifdef I2CDEV_SERIAL_DEBUG
//        Serial.println(". Done.");
//    #endif
//    return status == 0;
//}
//
///** Default timeout value for read operations.
// * Set this to 0 to disable timeout detection.
// */
//uint16_t I2Cdev::readTimeout = I2CDEV_DEFAULT_READ_TIMEOUT;
//
//#if I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
//    /*
//    FastWire 0.1
//    This is a library to help faster programs to read I2C devices.
//    Copyright(C) 2011 Francesco Ferrara
//    occhiobello at gmail dot com
//    */
//
//    boolean Fastwire::waitInt() {
//        int l = 250;
//        while (!(TWCR & (1 << TWINT)) && l-- > 0);
//        return l > 0;
//    }
//
//    void Fastwire::setup(int khz, boolean pullup) {
//        TWCR = 0;
//        // TODO: add support for other MCUs, this is ATmega328+compatible only
//        if (pullup)
//            PORTC |= ((1 << 4) | (1 << 5));
//        else
//            PORTC &= ~((1 << 4) | (1 << 5));
//
//        TWSR = 0; // no prescaler => prescaler = 1
//        TWBR = ((16000L / khz) - 16) / 2; // change the I2C clock rate
//        TWCR = 1 << TWEN; // enable twi module, no interrupt
//    }
//
//    byte Fastwire::write(byte device, byte address, byte value) {
//        byte twst, retry;
//        retry = 2;
//        do {
//            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO) | (1 << TWSTA);
//            if (!waitInt()) return 1;
//            twst = TWSR & 0xF8;
//            if (twst != TW_START && twst != TW_REP_START) return 2;
//
//            TWDR = device & 0xFE; // send device address without read bit (1)
//            TWCR = (1 << TWINT) | (1 << TWEN);
//            if (!waitInt()) return 3;
//            twst = TWSR & 0xF8;
//        }
//        while (twst == TW_MT_SLA_NACK && retry-- > 0);
//        if (twst != TW_MT_SLA_ACK) return 4;
//
//        TWDR = address; // send data to the previously addressed device
//        TWCR = (1 << TWINT) | (1 << TWEN);
//        if (!waitInt()) return 5;
//        twst = TWSR & 0xF8;
//        if (twst != TW_MT_DATA_ACK) return 6;
//
//        TWDR = value; // send data to the previously addressed device
//        TWCR = (1 << TWINT) | (1 << TWEN);
//        if (!waitInt()) return 7;
//        twst = TWSR & 0xF8;
//        if (twst != TW_MT_DATA_ACK) return 8;
//
//        return 0;
//    }
//
//    byte Fastwire::readBuf(byte device, byte address, byte *data, byte num) {
//        byte twst, retry;
//
//        retry = 2;
//        do {
//            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO) | (1 << TWSTA);
//            if (!waitInt()) return 16;
//            twst = TWSR & 0xF8;
//            if (twst != TW_START && twst != TW_REP_START) return 17;
//
//            TWDR = device & 0xFE; // send device address to write
//            TWCR = (1 << TWINT) | (1 << TWEN);
//            if (!waitInt()) return 18;
//            twst = TWSR & 0xF8;
//        }
//        while (twst == TW_MT_SLA_NACK && retry-- > 0);
//        if (twst != TW_MT_SLA_ACK) return 19;
//
//        TWDR = address; // send data to the previously addressed device
//        TWCR = (1 << TWINT) | (1 << TWEN);
//        if (!waitInt()) return 20;
//        twst = TWSR & 0xF8;
//        if (twst != TW_MT_DATA_ACK) return 21;
//
//        retry = 2;
//        do {
//            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO) | (1 << TWSTA);
//            if (!waitInt()) return 22;
//            twst = TWSR & 0xF8;
//            if (twst != TW_START && twst != TW_REP_START) return 23;
//
//            TWDR = device | 0x01; // send device address with the read bit (1)
//            TWCR = (1 << TWINT) | (1 << TWEN);
//            if (!waitInt()) return 24;
//            twst = TWSR & 0xF8;
//        }
//        while (twst == TW_MR_SLA_NACK && retry-- > 0);
//        if (twst != TW_MR_SLA_ACK) return 25;
//
//        for (uint8_t i = 0; i < num; i++) {
//            if (i == num - 1)
//              TWCR = (1 << TWINT) | (1 << TWEN);
//            else
//              TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWEA);
//            if (!waitInt()) return 26;
//            twst = TWSR & 0xF8;
//            if (twst != TW_MR_DATA_ACK && twst != TW_MR_DATA_NACK) return twst;
//            data[i] = TWDR;
//        }
//
//        return 0;
//    }
//#endif
//
//#if I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_NBWIRE
//    // NBWire implementation based heavily on code by Gene Knight <Gene@Telobot.com>
//    // Originally posted on the Arduino forum at http://arduino.cc/forum/index.php/topic,70705.0.html
//    // Originally offered to the i2cdevlib project at http://arduino.cc/forum/index.php/topic,68210.30.html
//
//    /*
//    call this version 1.0
//
//    Offhand, the only funky part that I can think of is in nbrequestFrom, where the buffer
//    length and index are set *before* the data is actually read. The problem is that these
//    are variables local to the TwoWire object, and by the time we actually have read the
//    data, and know what the length actually is, we have no simple access to the object's
//    variables. The actual bytes read *is* given to the callback function, though.
//
//    The ISR code for a slave receiver is commented out. I don't have that setup, and can't
//    verify it at this time. Save it for 2.0!
//
//    The handling of the read and write processes here is much like in the demo sketch code:
//    the process is broken down into sequential functions, where each registers the next as a
//    callback, essentially.
//
//    For example, for the Read process, twi_read00 just returns if TWI is not yet in a
//    ready state. When there's another interrupt, and the interface *is* ready, then it
//    sets up the read, starts it, and registers twi_read01 as the function to call after
//    the *next* interrupt. twi_read01, then, just returns if the interface is still in a
//    "reading" state. When the reading is done, it copies the information to the buffer,
//    cleans up, and calls the user-requested callback function with the actual number of
//    bytes read.
//
//    The writing is similar.
//
//    Questions, comments and problems can go to Gene@Telobot.com.
//
//    Thumbs Up!
//    Gene Knight
//
//    */
//
//    uint8_t TwoWire::rxBuffer[NBWIRE_BUFFER_LENGTH];
//    uint8_t TwoWire::rxBufferIndex = 0;
//    uint8_t TwoWire::rxBufferLength = 0;
//
//    uint8_t TwoWire::txAddress = 0;
//    uint8_t TwoWire::txBuffer[NBWIRE_BUFFER_LENGTH];
//    uint8_t TwoWire::txBufferIndex = 0;
//    uint8_t TwoWire::txBufferLength = 0;
//
//    //uint8_t TwoWire::transmitting = 0;
//    void (*TwoWire::user_onRequest)(void);
//    void (*TwoWire::user_onReceive)(int);
//
//    static volatile uint8_t twi_transmitting;
//    static volatile uint8_t twi_state;
//    static uint8_t twi_slarw;
//    static volatile uint8_t twi_error;
//    static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
//    static volatile uint8_t twi_masterBufferIndex;
//    static uint8_t twi_masterBufferLength;
//    static uint8_t twi_rxBuffer[TWI_BUFFER_LENGTH];
//    static volatile uint8_t twi_rxBufferIndex;
//    //static volatile uint8_t twi_Interrupt_Continue_Command;
//    static volatile uint8_t twi_Return_Value;
//    static volatile uint8_t twi_Done;
//    void (*twi_cbendTransmissionDone)(int);
//    void (*twi_cbreadFromDone)(int);
//
//    void twi_init() {
//        // initialize state
//        twi_state = TWI_READY;
//
//        // activate internal pull-ups for twi
//        // as per note from atmega8 manual pg167
//        sbi(PORTC, 4);
//        sbi(PORTC, 5);
//
//        // initialize twi prescaler and bit rate
//        cbi(TWSR, TWPS0); // TWI Status Register - Prescaler bits
//        cbi(TWSR, TWPS1);
//
//        /* twi bit rate formula from atmega128 manual pg 204
//        SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
//        note: TWBR should be 10 or higher for master mode
//        It is 72 for a 16mhz Wiring board with 100kHz TWI */
//
//        TWBR = ((CPU_FREQ / TWI_FREQ) - 16) / 2; // bitrate register
//        // enable twi module, acks, and twi interrupt
//
//        TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
//
//        /* TWEN - TWI Enable Bit
//        TWIE - TWI Interrupt Enable
//        TWEA - TWI Enable Acknowledge Bit
//        TWINT - TWI Interrupt Flag
//        TWSTA - TWI Start Condition
//        */
//    }
//
//    typedef struct {
//        uint8_t address;
//        uint8_t* data;
//        uint8_t length;
//        uint8_t wait;
//        uint8_t i;
//    } twi_Write_Vars;
//
//    twi_Write_Vars *ptwv = 0;
//    static void (*fNextInterruptFunction)(void) = 0;
//
//    void twi_Finish(byte bRetVal) {
//        if (ptwv) {
//            free(ptwv);
//            ptwv = 0;
//        }
//        twi_Done = 0xFF;
//        twi_Return_Value = bRetVal;
//        fNextInterruptFunction = 0;
//    }
//
//    uint8_t twii_WaitForDone(uint16_t timeout) {
//        uint32_t endMillis = millis() + timeout;
//        while (!twi_Done && (timeout == 0 || millis() < endMillis)) continue;
//        return twi_Return_Value;
//    }
//
//    void twii_SetState(uint8_t ucState) {
//        twi_state = ucState;
//    }
//
//    void twii_SetError(uint8_t ucError) {
//        twi_error = ucError ;
//    }
//
//    void twii_InitBuffer(uint8_t ucPos, uint8_t ucLength) {
//        twi_masterBufferIndex = 0;
//        twi_masterBufferLength = ucLength;
//    }
//
//    void twii_CopyToBuf(uint8_t* pData, uint8_t ucLength) {
//        uint8_t i;
//        for (i = 0; i < ucLength; ++i) {
//            twi_masterBuffer[i] = pData[i];
//        }
//    }
//
//    void twii_CopyFromBuf(uint8_t *pData, uint8_t ucLength) {
//        uint8_t i;
//        for (i = 0; i < ucLength; ++i) {
//            pData[i] = twi_masterBuffer[i];
//        }
//    }
//
//    void twii_SetSlaRW(uint8_t ucSlaRW) {
//        twi_slarw = ucSlaRW;
//    }
//
//    void twii_SetStart() {
//        TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
//    }
//
//    void twi_write01() {
//        if (TWI_MTX == twi_state) return; // blocking test
//        twi_transmitting = 0 ;
//        if (twi_error == 0xFF)
//            twi_Finish (0);    // success
//        else if (twi_error == TW_MT_SLA_NACK)
//            twi_Finish (2);    // error: address send, nack received
//        else if (twi_error == TW_MT_DATA_NACK)
//            twi_Finish (3);    // error: data send, nack received
//        else
//            twi_Finish (4);    // other twi error
//        if (twi_cbendTransmissionDone) return twi_cbendTransmissionDone(twi_Return_Value);
//        return;
//    }
//
//
//    void twi_write00() {
//        if (TWI_READY != twi_state) return; // blocking test
//        if (TWI_BUFFER_LENGTH < ptwv -> length) {
//            twi_Finish(1); // end write with error 1
//            return;
//        }
//        twi_Done = 0x00; // show as working
//        twii_SetState(TWI_MTX); // to transmitting
//        twii_SetError(0xFF); // to No Error
//        twii_InitBuffer(0, ptwv -> length); // pointer and length
//        twii_CopyToBuf(ptwv -> data, ptwv -> length); // get the data
//        twii_SetSlaRW((ptwv -> address << 1) | TW_WRITE); // write command
//        twii_SetStart(); // start the cycle
//        fNextInterruptFunction = twi_write01; // next routine
//        return twi_write01();
//    }
//
//    void twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait) {
//        uint8_t i;
//        ptwv = (twi_Write_Vars *)malloc(sizeof(twi_Write_Vars));
//        ptwv -> address = address;
//        ptwv -> data = data;
//        ptwv -> length = length;
//        ptwv -> wait = wait;
//        fNextInterruptFunction = twi_write00;
//        return twi_write00();
//    }
//
//    void twi_read01() {
//        if (TWI_MRX == twi_state) return; // blocking test
//        if (twi_masterBufferIndex < ptwv -> length) ptwv -> length = twi_masterBufferIndex;
//        twii_CopyFromBuf(ptwv -> data, ptwv -> length);
//        twi_Finish(ptwv -> length);
//        if (twi_cbreadFromDone) return twi_cbreadFromDone(twi_Return_Value);
//        return;
//    }
//
//    void twi_read00() {
//        if (TWI_READY != twi_state) return; // blocking test
//        if (TWI_BUFFER_LENGTH < ptwv -> length) twi_Finish(0); // error return
//        twi_Done = 0x00; // show as working
//        twii_SetState(TWI_MRX); // reading
//        twii_SetError(0xFF); // reset error
//        twii_InitBuffer(0, ptwv -> length - 1); // init to one less than length
//        twii_SetSlaRW((ptwv -> address << 1) | TW_READ); // read command
//        twii_SetStart(); // start cycle
//        fNextInterruptFunction = twi_read01;
//        return twi_read01();
//    }
//
//    void twi_readFrom(uint8_t address, uint8_t* data, uint8_t length) {
//        uint8_t i;
//
//        ptwv = (twi_Write_Vars *)malloc(sizeof(twi_Write_Vars));
//        ptwv -> address = address;
//        ptwv -> data = data;
//        ptwv -> length = length;
//        fNextInterruptFunction = twi_read00;
//        return twi_read00();
//    }
//
//    void twi_reply(uint8_t ack) {
//        // transmit master read ready signal, with or without ack
//        if (ack){
//            TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA);
//        } else {
//            TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT);
//        }
//    }
//
//    void twi_stop(void) {
//        // send stop condition
//        TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTO);
//
//        // wait for stop condition to be exectued on bus
//        // TWINT is not set after a stop condition!
//        while (TWCR & _BV(TWSTO)) {
//            continue;
//        }
//
//        // update twi state
//        twi_state = TWI_READY;
//    }
//
//    void twi_releaseBus(void) {
//        // release bus
//        TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);
//
//        // update twi state
//        twi_state = TWI_READY;
//    }
//
//    SIGNAL(TWI_vect) {
//        switch (TW_STATUS) {
//            // All Master
//            case TW_START:     // sent start condition
//            case TW_REP_START: // sent repeated start condition
//                // copy device address and r/w bit to output register and ack
//                TWDR = twi_slarw;
//                twi_reply(1);
//                break;
//
//            // Master Transmitter
//            case TW_MT_SLA_ACK:  // slave receiver acked address
//            case TW_MT_DATA_ACK: // slave receiver acked data
//                // if there is data to send, send it, otherwise stop
//                if (twi_masterBufferIndex < twi_masterBufferLength) {
//                    // copy data to output register and ack
//                    TWDR = twi_masterBuffer[twi_masterBufferIndex++];
//                    twi_reply(1);
//                } else {
//                    twi_stop();
//                }
//                break;
//
//            case TW_MT_SLA_NACK:  // address sent, nack received
//                twi_error = TW_MT_SLA_NACK;
//                twi_stop();
//                break;
//
//            case TW_MT_DATA_NACK: // data sent, nack received
//                twi_error = TW_MT_DATA_NACK;
//                twi_stop();
//                break;
//
//            case TW_MT_ARB_LOST: // lost bus arbitration
//                twi_error = TW_MT_ARB_LOST;
//                twi_releaseBus();
//                break;
//
//            // Master Receiver
//            case TW_MR_DATA_ACK: // data received, ack sent
//                // put byte into buffer
//                twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
//
//            case TW_MR_SLA_ACK:  // address sent, ack received
//                // ack if more bytes are expected, otherwise nack
//                if (twi_masterBufferIndex < twi_masterBufferLength) {
//                    twi_reply(1);
//                } else {
//                    twi_reply(0);
//                }
//                break;
//
//            case TW_MR_DATA_NACK: // data received, nack sent
//                // put final byte into buffer
//                twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
//
//            case TW_MR_SLA_NACK: // address sent, nack received
//                twi_stop();
//                break;
//
//        // TW_MR_ARB_LOST handled by TW_MT_ARB_LOST case
//
//        // Slave Receiver (NOT IMPLEMENTED YET)
//        /*
//            case TW_SR_SLA_ACK:   // addressed, returned ack
//            case TW_SR_GCALL_ACK: // addressed generally, returned ack
//            case TW_SR_ARB_LOST_SLA_ACK:   // lost arbitration, returned ack
//            case TW_SR_ARB_LOST_GCALL_ACK: // lost arbitration, returned ack
//                // enter slave receiver mode
//                twi_state = TWI_SRX;
//
//                // indicate that rx buffer can be overwritten and ack
//                twi_rxBufferIndex = 0;
//                twi_reply(1);
//                break;
//
//            case TW_SR_DATA_ACK:       // data received, returned ack
//            case TW_SR_GCALL_DATA_ACK: // data received generally, returned ack
//                // if there is still room in the rx buffer
//                if (twi_rxBufferIndex < TWI_BUFFER_LENGTH) {
//                    // put byte in buffer and ack
//                    twi_rxBuffer[twi_rxBufferIndex++] = TWDR;
//                    twi_reply(1);
//                } else {
//                    // otherwise nack
//                    twi_reply(0);
//                }
//                break;
//
//            case TW_SR_STOP: // stop or repeated start condition received
//                // put a null char after data if there's room
//                if (twi_rxBufferIndex < TWI_BUFFER_LENGTH) {
//                    twi_rxBuffer[twi_rxBufferIndex] = 0;
//                }
//
//                // sends ack and stops interface for clock stretching
//                twi_stop();
//
//                // callback to user defined callback
//                twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex);
//
//                // since we submit rx buffer to "wire" library, we can reset it
//                twi_rxBufferIndex = 0;
//
//                // ack future responses and leave slave receiver state
//                twi_releaseBus();
//                break;
//
//            case TW_SR_DATA_NACK:       // data received, returned nack
//            case TW_SR_GCALL_DATA_NACK: // data received generally, returned nack
//                // nack back at master
//                twi_reply(0);
//                break;
//
//            // Slave Transmitter
//            case TW_ST_SLA_ACK:          // addressed, returned ack
//            case TW_ST_ARB_LOST_SLA_ACK: // arbitration lost, returned ack
//                // enter slave transmitter mode
//                twi_state = TWI_STX;
//
//                // ready the tx buffer index for iteration
//                twi_txBufferIndex = 0;
//
//                // set tx buffer length to be zero, to verify if user changes it
//                twi_txBufferLength = 0;
//
//                // request for txBuffer to be filled and length to be set
//                // note: user must call twi_transmit(bytes, length) to do this
//                twi_onSlaveTransmit();
//
//                // if they didn't change buffer & length, initialize it
//                if (0 == twi_txBufferLength) {
//                    twi_txBufferLength = 1;
//                    twi_txBuffer[0] = 0x00;
//                }
//
//                // transmit first byte from buffer, fall through
//
//            case TW_ST_DATA_ACK: // byte sent, ack returned
//                // copy data to output register
//                TWDR = twi_txBuffer[twi_txBufferIndex++];
//
//                // if there is more to send, ack, otherwise nack
//                if (twi_txBufferIndex < twi_txBufferLength) {
//                    twi_reply(1);
//                } else {
//                    twi_reply(0);
//                }
//                break;
//
//            case TW_ST_DATA_NACK: // received nack, we are done
//            case TW_ST_LAST_DATA: // received ack, but we are done already!
//                // ack future responses
//                twi_reply(1);
//                // leave slave receiver state
//                twi_state = TWI_READY;
//                break;
//            */
//
//            // all
//            case TW_NO_INFO:   // no state information
//                break;
//
//            case TW_BUS_ERROR: // bus error, illegal stop/start
//                twi_error = TW_BUS_ERROR;
//                twi_stop();
//                break;
//        }
//
//        if (fNextInterruptFunction) return fNextInterruptFunction();
//    }
//
//    TwoWire::TwoWire() { }
//
//    void TwoWire::begin(void) {
//        rxBufferIndex = 0;
//        rxBufferLength = 0;
//
//        txBufferIndex = 0;
//        txBufferLength = 0;
//
//        twi_init();
//    }
//
//    void TwoWire::beginTransmission(uint8_t address) {
//        //beginTransmission((uint8_t)address);
//
//        // indicate that we are transmitting
//        twi_transmitting = 1;
//
//        // set address of targeted slave
//        txAddress = address;
//
//        // reset tx buffer iterator vars
//        txBufferIndex = 0;
//        txBufferLength = 0;
//    }
//
//    uint8_t TwoWire::endTransmission(uint16_t timeout) {
//        // transmit buffer (blocking)
//        //int8_t ret =
//        twi_cbendTransmissionDone = NULL;
//        twi_writeTo(txAddress, txBuffer, txBufferLength, 1);
//        int8_t ret = twii_WaitForDone(timeout);
//
//        // reset tx buffer iterator vars
//        txBufferIndex = 0;
//        txBufferLength = 0;
//
//        // indicate that we are done transmitting
//        // twi_transmitting = 0;
//        return ret;
//    }
//
//    void TwoWire::nbendTransmission(void (*function)(int)) {
//        twi_cbendTransmissionDone = function;
//        twi_writeTo(txAddress, txBuffer, txBufferLength, 1);
//        return;
//    }
//
//    void TwoWire::send(uint8_t data) {
//        if (twi_transmitting) {
//            // in master transmitter mode
//            // don't bother if buffer is full
//            if (txBufferLength >= NBWIRE_BUFFER_LENGTH) {
//                return;
//            }
//
//            // put byte in tx buffer
//            txBuffer[txBufferIndex] = data;
//            ++txBufferIndex;
//
//            // update amount in buffer
//            txBufferLength = txBufferIndex;
//        } else {
//            // in slave send mode
//            // reply to master
//            //twi_transmit(&data, 1);
//        }
//    }
//
//    uint8_t TwoWire::receive(void) {
//        // default to returning null char
//        // for people using with char strings
//        uint8_t value = 0;
//
//        // get each successive byte on each call
//        if (rxBufferIndex < rxBufferLength) {
//            value = rxBuffer[rxBufferIndex];
//            ++rxBufferIndex;
//        }
//
//        return value;
//    }
//
//    uint8_t TwoWire::requestFrom(uint8_t address, int quantity, uint16_t timeout) {
//        // clamp to buffer length
//        if (quantity > NBWIRE_BUFFER_LENGTH) {
//            quantity = NBWIRE_BUFFER_LENGTH;
//        }
//
//        // perform blocking read into buffer
//        twi_cbreadFromDone = NULL;
//        twi_readFrom(address, rxBuffer, quantity);
//        uint8_t read = twii_WaitForDone(timeout);
//
//        // set rx buffer iterator vars
//        rxBufferIndex = 0;
//        rxBufferLength = read;
//
//        return read;
//    }
//
//    void TwoWire::nbrequestFrom(uint8_t address, int quantity, void (*function)(int)) {
//        // clamp to buffer length
//        if (quantity > NBWIRE_BUFFER_LENGTH) {
//            quantity = NBWIRE_BUFFER_LENGTH;
//        }
//
//        // perform blocking read into buffer
//        twi_cbreadFromDone = function;
//        twi_readFrom(address, rxBuffer, quantity);
//        //uint8_t read = twii_WaitForDone();
//
//        // set rx buffer iterator vars
//        //rxBufferIndex = 0;
//        //rxBufferLength = read;
//
//        rxBufferIndex = 0;
//        rxBufferLength = quantity; // this is a hack
//
//        return; //read;
//    }
//
//    uint8_t TwoWire::available(void) {
//        return rxBufferLength - rxBufferIndex;
//    }
//
//#endif
